U.S. patent number 4,733,916 [Application Number 06/877,898] was granted by the patent office on 1988-03-29 for bending line along overlapping layers in folding box.
Invention is credited to Gerhard Seufert.
United States Patent |
4,733,916 |
Seufert |
March 29, 1988 |
Bending line along overlapping layers in folding box
Abstract
In a folding box consisting of a cardboard blank part (1) and a
plastic foil blank part (3) glued thereto, thinned-down areas (17)
are placed in the foil blank part (3) at the overlap spots between
the two blank parts in the area of the box edges, which directly
adjoin the bend lines (13) and extend at least across the overlap
length. The thinned-down areas (17) compensate stresses arising in
the foil material at the overlap spots during folding, this
compensation being by deformation, without which the cardboard
material is stretched at the edge overlap spots so that it
tears.
Inventors: |
Seufert; Gerhard (6054 Rodgau
5, DE) |
Family
ID: |
25833603 |
Appl.
No.: |
06/877,898 |
Filed: |
June 24, 1986 |
Foreign Application Priority Data
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Jun 29, 1985 [DE] |
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3523416 |
Feb 20, 1986 [DE] |
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3605413 |
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Current U.S.
Class: |
229/162.7;
229/920; 229/930 |
Current CPC
Class: |
B65D
5/4204 (20130101); B65D 5/4266 (20130101); Y10S
229/92 (20130101); Y10S 229/93 (20130101) |
Current International
Class: |
B65D
5/42 (20060101); B65D 025/54 () |
Field of
Search: |
;229/162,DIG.4
;206/45.31,45.34 ;220/82R,339,377 ;156/108 ;493/905,944
;428/167,172 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1436993 |
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Jul 1969 |
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DE |
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2507155 |
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Jun 1981 |
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FR |
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2090230 |
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Jul 1982 |
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GB |
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Primary Examiner: Marcus; Stephen
Assistant Examiner: Elkins; Gary E.
Attorney, Agent or Firm: Toren, McGeady & Associates
Claims
What is claimed is:
1. A folding box consisting of a first cut-to-size blank from
non-transparent material, and a second cut-to-size blank from
transparent stiff plastic foil, which extends over at least one box
edge, a bending line provided in the plastic foil, second blank
overlapping and being glued to the first cut-to-size blank on an
inside surface of said first blank, wherein the overlap between the
first and the second cut-to-size glanks exists also at at least one
end of the bending line, and the bending line is continued in the
first cut-to-size blank by a corresponding groove line, the bending
line and groove line being approximately the same width and wherein
a box edge of two box walls is formed by said bending line and said
groove line, characterized in that the second blank is thinned-down
to a fraction of the thickness of remaining portions of the second
blank in an area along the bending line and directly adjacent to
the bending line at the overlap between the first and the second
blanks, the thinned-down area of the second blank extending over
the entire width of the overlap.
2. Folding box according to claim 1, characterized in that each of
the thinned-down areas has a cross-section remaining essentially
constant over a length of the respective thinned-down area.
3. Folding box according to claim 1 or 2, characterized in that
each of the thinned-down areas has a diminishing thickness starting
from a side edge towards a center thereof, wherein the thickness in
the region of the groove lines of the first blank is smallest.
4. Folding box according to claim 3, characterized in that the
thinned-down areas are delimited on one side of said second blank
in an arc-shaped fashion when viewed in cross-section.
5. Folding box according to claim 3, characterized in that the
thinned-down areas are delimited on one side of said second blank,
respectively, by at least two abutting inclined surfaces.
6. Folding box according to claim 3, characterized in that the
thinned-down areas are delimited on one side of said second blank,
respectively, by two external inclined surfaces and a central flat
surface.
7. Folding box according to claim 3, characterized in that the
thinned-down areas are delimited on one side of said second blank
by flat surfaces arranged in a step-shaped manner.
8. Folding box according to claim 7 or 2, characterized in that,
respectively, three parallel grooves are formed equally spaced
within each of the thinned-down areas, a central one of said three
grooves being arranged in the second blank in a direction of
extension of said bend line associated with the respective
thinned-down area.
9. Folding box according to claim 8, characterized in that the
central groove adjoins directly the associated bend line, and the
others of said three grooves bend, respectively, at inner ends
thereof and unite with the cnetral groove at a junction point with
the associated bend line.
10. Folding box according to claim 8, characterized in that the
central groove is pressed up to a smaller foil residual thickness
into the thinned-down foil than the others of said three grooves,
which are pressed in up to an equal foil residual thickness.
11. Folding box according to claim 10 or 2, characterized in that a
minimum thickness in each of the thinned-down areas amounts to
approximately 100 .mu.m with a thickness of the plastic foil used
for the second blank of between 200 and 400 .mu.m.
12. Folding box according to the claim 10, characterized in that
the foil residual thickness at the central groove amounts to about
one-third and the foil residual thickness at the two other grooves
amounts to about two-thirds of a minimum thickness in each of the
thinned-down areas.
13. Folding box according to claim 12 or 2, characterized in that
the gluing, between the two blanks, ends approximately at a side
edge of each of the thinned-down areas.
14. Folding box according to claim 8, characterized in that the
gluing, between the two blanks, ends at said other two grooves.
15. Folding box according to 14 or 2, characterized in that the
thinned-down areas are produced by an operation on one side of the
plastic foil.
16. Folding box according to claim 15 or 2, characterized in that
the thinned-down areas together with the bend line are produced by
high frequency-/pressure application or by hot stamping.
17. Folding box according to claim 16 or 2, characterized in that
each of the thinned-down areas comprises, respectively, one central
strip covering the associated groove line of the first blank and
adjoining the associated bend line of the second blank, which has a
constant foil residual thickness throughout and which is adjoined
in a continuous manner by transition surfaces which are concave and
which reach up to side edges of the respective thinned-down
area.
18. Folding box according to claim 17, characterized in that the
central strip foil residual thickness is approximately 40 to 60
.mu.m with a thickness of the plastics foil utilized for the second
blank of between approximately 200 and 400 .mu.m, while a width of
the central strip amounts to approximately 1/3 to 1/6 of a width of
each thinned-down area.
19. Folding box according to claim 18 or 2, characterized in that,
respectively, one separation extending throughout the material
thickness is provided across each bend adjacent to the respective
thinned-down area in the second blank, said separation being
essentially not overlapped by the first blank.
20. Folding box according to claim 19, characterized in that each
separation is constituted as a line-shaped incision extending
transversely to the bend line, said incision projecting on opposite
sides of the bend line, a length of said incision being
approximately equivalent to a width of the thinned-down area, and
said incision extending parallel to an edge of the first blank in
close proximity.
21. Folding box according to claim 19, characterized in that each
separation is designed as a hole cutout, which projects on opposite
sides of the bend line with approximately equal area regions and a
width of said hole cutout corresponds, at most, to a width of the
thinned-down area.
22. Folding box according to claim 21, characterized in that the
hole cutout is designed to be circularly shaped in the second blank
when the second blank is in a flat resting position.
23. Folding box according to claim 21, characterized in that the
hole cutout is designed to be elliptically shaped in the second
blank when the second blank is in a flat resting position, a longer
axis of said elliptically shaped cutout extending parallel to an
adjacent edge of the first blank.
24. Folding box according to claim 1, wherein said first blank has
a plurality of groove lines and said second blank correspondingly
has a plurality of bend lines and thinned-down areas.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a folding box, consisting of a first
cut-to-size blank from non-transparent material, particularly
cardboard, and a second cut-to-size blank from transparent stiff
plastic foil, which extends over at least one box edge which, in
one portion, is constituted by a bending line provided in the
plastic foil, and which is glued with the first cut-to-size blank
overlapping on its inside; an overlap between the first and second
cut-to-size blank exists also at at least one end of the bending
line and the bending line is continued in the first cut-to-size
part by a corresponding groove line, at which the box edge to the
other part is formed.
2. Description of the Related Art
Such folding boxes consisting of differing materials are known in
different embodiments. In a known window folding box, the cardboard
cut-to-size part has an aperture constituting a viewing window,
which is sealed by a leaf of stiff plastic (DE-OS No. 31 48 443).
In another known folding packing (DE No. 31 53 240 of the
International Application WO No. 82/00449), not only is a viewing
window in the cardboard blank provided, but a plurality of walls or
wall portions connected with each other by box edges possibly
including adjacent sealing flaps and dust strips are fabricated
completely from a plastic part.
In the two box types described above, overlaps between the two
blanks consisting of differing materials exist at the end of
bending lines formed in the plastic blank, or can exist in the
previously described folding packing.
These points of overlap cause difficulties during folding, since,
because of the double material thickness at the points of overlap,
material displacement and material stretching can occur. Since the
plastic blank rests on the inside of the cardboard blank, the
plastics foil is crushed during folding in the area of the groove
line of the cardboard blank, while the cardboard is simultaneously
stretched in such a way that its outer layer or liming can tear
along the groove line. The folding at such overlap points can be
performed mechanically only in an unsatisfactory manner.
It is provided for avoidance of the previously described
difficulties in an additional known folding container with window
(DE-OS No. 14 36 993), that recesses are provided in the window
foil edge in the area of the bending line, while tangs or fingers
are provided at the cardboard blank which overlap these recesses.
Since the overlapping surfaces at the fingers and the window foil
are free of glue in this area, a displacement between these
surfaces during folding is possible without the occurrence of
stresses. At the same time the folding container does not become
leaky at the recesses, since the tangs cause a covering in the area
of the container edges. The tangs or fingers existing in this known
folding container, however, not only considerable limit the shaping
possibilities of the container, but also render the mechanical
folding more difficult, because they bend outwards during the
folding process and thus form undesirable protrusions.
In the previously mentioned known window folding box (DE-OS No. 31
48 443), it is provided that the above-mentioned recesses or
notches extend at least up to the edge of the window opening.
Because of the more or less large apertures thus formed between the
cardboard blank and the plastics leaf in the area of each overlap
spot at the box edges, material displacement in these difficult
areas should not occur during the folding process. The existence of
apertures at folding box edges is, however, not acceptable for all
applications of packagings of this type.
SUMMARY OF THE INVENTION
The present invention provides a folding box of the previously
discussed species, in which neither outwardly projecting tangs nor
apertures exist at the overlap spots in the area of the folding box
edges and which, in spite of that, can be mechanically folded
without difficulty also at these overlap spots. The task thus
defined is solved in the invention, in that at the overlap spots
between the first and the second blank existing in the area of the
box edges, the second blank is thinned down in a shaped manner to a
fraction of its original foil thickness directly adjacent to the
bending lines, and that the thinned-down areas of the second blank
extend at least over the overlap length.
These measures result in a complete stress equalization at the
explained difficult areas of the overlap spots located at the box
edges, because the thinned-down areas are easy to deform under the
action of the upsetting forces generated during folding. These
deformations, which essentially occur as small creases exclusively
in the area of the thinned-down areas, are located on the inside of
the groove lines of the cardboard blank and therefore are not
observable in an undesirable fashion from the outside. If the
thinned-down areas are dimensioned in such a manner that they
extend only over the overlap length or possibly are slightly
larger, meaning that they do not protrude at all, or only slightly,
beyond the cardboard edge, a smooth and continuous edge without
interruptions is obtained when folding the box edge involved, which
contains neither holes nor steps at those points where the two
different materials abut which would be visible from the
outside.
The thinned-down areas appropriately exhibit an essentially
constant cross-section across their length. Thus a uniform stress
equalization over their length is achieved in the form of
continuous small creases, if the folding box is folded at the edges
involved, that is, when it is errected from its flat collapsed
position.
The thinned-down areas comprise, advantageously, a diminishing
thickness starting from their side edges towards the center,
wherein the thickness is smallest in the area of the groove lines
in the first blank. The deformability of the thinned-down areas
along the groove lines of the first blank is largest because of
these measures, wherein the formation of small creases equalizing
the stress is favored.
The thinned-down areas, which naturally are produced in the plastic
foil blank prior to its being united with the cardboard blank by
gluing, can be produced by action on the plastic foil from both
sides. Preferably, however, they are produced by action only on one
side of the plastic foil, while the plastic foil part is resting on
a flat surface.
Especially suitable thinned-down areas for the task provided are
achieved if these are produced together with the fold lines by high
frequency-/pressure action or by hot stamping Attention has to be
paid when forming the thinned-down areas so that no interfering
migration beads, consisting of plastics material, are generated at
the side edges of the thinned-down areas, so that a gluing with a
cardboard blank is also possible on that foil side at which such
migration beads could be formed.
Pursuing the inventive thought, the thinned-down areas can be
differently shaped while retaining the same, or nearly the same,
effectiveness. Preferably, the thinned-down areas are bounded on
one side in an arc-shaped manner viewed in cross-section. They can,
however, also be bounded on one side respectively by at least two
abutting inclined planes. Another possibility consists in that the
thinned-down areas are bounded on one side, respectively, by two
outer inclined planes and one central flat plane. Finally, an
embodiment is also possible in which they are bounded on one side
by flat faces arranged in a step-shaped manner.
It is provided in a preferred embodiment of the folding box that,
respectively, three parallel grooves are molded spaced equally
within the thinned-down areas, the central groove being arranged in
direction of extension of the appropriate bending line in the
second blank. These fine grooves create intended folding points, at
which small uniform wrinkles are generated when folding the folding
box, which take care of the required stress equalization and which
extend parallel to the neighboring groove lines in the first
blank.
It is advantageous here if the central groove follows directly upon
the bend line, and the two side grooves extend, respectively kinked
at their inner ends and unite with the central groove at the
junction point to form the bend line. Because of this groove
configuration, the stresses occurring during folding of the box
also at the transition between the bend line in the plastic foil
and the thinned-down area, are compensated by a roof-like
deformation of the small surface areas of the thinneddown area
bounded by the three converging grooves.
Particularly good results are achieved in the formation of small
predetermined wrinkles in the overlapping edge area if the central
groove is pressed into the thinned-down foil up to a smaller foil
residual thickness than the two side grooves, which are pressed in
up to an equal foil residual thickness.
With a thickness of between 200 .mu.m and 400 .mu.m of the plastic
foil used for the second blank, it has been shown to be
advantageous if the minimum thickness in the region of the
thinned-down areas amounts to about 100 .mu.m.
It is appropriate for achieving good folding at the critical edge
overlapping zones of the two differing materials, if the foil
residual thickness at the central groove amounts to about one-third
and the foil residual thickness of the two side grooves to about
two-thirds of the minimum thickness in the region of the
thinned-down areas.
It is advantageous for the desired formation of small wrinkles from
the thinned-down areas along the groove lines in the cardboard
blank, if the overlap gluing between the two blankds ends
approximately at the side edges of the thinned-down areas. During
the placement of the three parallel grooves within the thinned-down
areas for the formation of such predetermined wrinkles, one has to
pay attention that the overlap gluing between the two blanks ends
at the side grooves.
Good results are also achieved if the thinned-down areas comprise,
respectively, one central strip covering the associated groove line
of the first blank and following upon the associated bend line of
the second blank; said central strip has a constant foil residual
thickness at all points and is adjoined in a stepless fashion by
transition planes which are arched in concave manner on the sides
and which reach up to the side edges. If in this case the central
strip has a foil residual thickness of approximately 40 to 60 .mu.m
with a thickness of the plastics foil used for the second blank of
approximately between 200 and 400 .mu.m, while its width amounts to
about 1/3 to 1/6 of the width of the thinned-down area,
particularly good results are achieved.
A folding box designed according to the invention can be folded
without problems, during box erection, at the overlapping places
located at the box edges defined by the groove lines in the first
blank and the bend lines in the second bank aligned with said
groove lines; this without the cardboard material of the first
blank tearing in the zone of the groove lines and also without
interfering deformation of the plastic foil constituting the second
blank appearing in an area open to view. Herein, all stresses
arising during the folding operation are compensated by the
thinned-down areas existing at the overlapping places.
Due to the manufacturing tolerances, above all during gluing of the
two blanks, displacements of the thinned-down areas with respect to
the first blank can occur under certain circumstances, which at the
boundary between the visible area and the overlapping places can
lead to residual stresses not completely compensated by the
thinned-down areas, particularly when thicker plastic foils of
roughly 400 .mu.m thickness are utilized. In order to be able to
also remove residual stresses of this kind, should this be required
in order to eliminate the stress effects on the cardboard material
and the foil visible zones adjacent to the overlapping places, it
is proposed according to a further refinement of the invention,
that at the junction place between the bend lines and the
thinned-down areas in the second blank, respectively, one
interruption be provided which is continuous throughout the
material thickness, and which, in essence, is not overlapped by the
first blank.
It has been shown that all possible residual stresses at the
boundaries between the visible area and the cardboard zone can be
absorbed by such breaks; this alleviates the possibility of the
cardboard tearing at the cardboard boundary as well as warping of
the adjacent foil regions. In its simplest form sufficient for most
of applications, the break is made advantageously to be a
line-shaped incision extending transversely to the bending line,
which incision projects on both sides beyond the bend line, has
approximately the width of the thinned-down area, and extends
parallel to the closely adjacent edge of the first blank. The
incision can hardly be seen from the outside and does not
constitute a hole worth mentioning in the foil material even in the
erected state of the box.
In cases where it is relatively unimportant whether any holes are
formed at the box edge in the visible area, an arrangement can be
made, according to a further embodiment of the invention, in such a
way that the break is designed as a hole cutout which projects, at
both sides, beyond the bend line with surface areas corresponding
approximately to each other and whose width corresponds to
approximately the width of the thinned-down area.
Particularly favorable stress equalization results are achieved by
this method if the hole cutout is designed to be circularly-shaped
in the flat resting second blank or if the hole cutout in the flat
resting second blank exhibits approximately the shape of an
ellipse, whose longer axis extends parallel to the adjacent edge of
the first blank.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described with particularity in the following with
the help of drawings illustrating the embodiment examples, in part,
schematically, wherein:
FIG. 1 is a perspective view of a window folding box blank
consisting of two parts glued to each other,
FIG. 2 is a plan view of a blank consisting also of two parts glued
to each other of another folding box type;
FIG. 3 is a partial magnified plan view of an ovelapping place with
a thinned-down area arranged in the plastic material blank, in a
flat resting position,
FIG. 4 is a plan view similar to FIG. 3 with parallel grooves
formed in the thinned-down area;
FIG. 5 is a cross-sectional view of the plastic material blank
taken along the line V--V in FIG. 3;
FIG. 6 is a corresponding cross-sectional view of the plastic
material blank taken along the line VI--VI in FIG. 4;
FIGS. 7 to 9 and 13 are cross-sectional views similar to those in
further embodiment shapes of the thinned-down areas;
FIG. 10 is a perspective view of a window corner of the glued,
erected and closed window folding box according to FIG. 1;
FIG. 11 is a partial side view of the folding box illustrated in
FIG. 10;
FIG. 12 is a cross-sectional magnified view of the folding box
taken along the line XII--XII in FIG. 11;
FIG. 14 is a partial and magnified inside view of an overlapping
place of a folding box blank composed of two blanks in a flat
resting position with a first embodiment of a break;
FIG. 15 is a partial side view of the folding box erected from the
folding box blank according to FIG. 14;
FIG. 16 is an inside view of an overlapping place of a folding box
blank similar to FIG. 14, with a second embodiment of the
break,
FIG. 17 is a partial perspective view of the folding box erected
from the folding box blank according to FIG. 16;
FIG. 18 is an inside view of an overlapping place of a folding box
blank similar to the FIGS. 14 and 16 with a third embodiment form
of the break; and
FIG. 19 is a partial perspective view of the folding box erected
from the folding box blank according to FIG. 18.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the magnified illustrations in the FIGS. 5 to 9, 12 and 13, the
thickness dimensions are shown considerably more magnified than the
width dimensions for reasons of clarity.
FIG. 1 shows a typical blank of a window folding box, which is
composed of a first blank portion 1 of cardboard defining the outer
contour of the blank and a second blank portion 3 from transparent
stiff plastic foil covering a window opening 2 in the cardboard
blank portion in an overlapping manner. The blank results, after
gluing, erection and sealing on both sides, in a cube-shaped window
folding box, whose window opening 2 extends across its front wall 4
and across partial regions of the side walls 5 and 6 adjacent
thereto. The rear wall 7, adjacent to the side wall 6, is part of
the cardboard blank portion 1 as well as four dust tabs 8 connected
to the side walls 5 and 6, and the sealing tabs 9 connected to the
front wall 4. Insert tabs 10 are connected to the sealing tabs 9. A
gluing tab 11 is provided at the rear wall 7 for gluing together of
the blank into a compact box jacket, the external face of gluing
tab 11 being glued to the inside face of the side wall 5. At the
interfaces between previously mentioned portions of the cardboard
blank portion 1, groove lines 12 are pressed into the cardboard,
which in turn, form the box edges after gluing, erecting and
closing of the folding box.
The foil blank 3 is glued to the inside surfaces of the front wall
4 and the side walls 5 and 6 so as to overlap the window opening 2
on all sides in a frame-like manner. The frame-like overlapping
surface is indicated in FIG. 1 with dots. The same applies to FIGS.
2-4. Naturally, the entire overlapping surface is not required for
gluing the two blank parts 1 and 3 together. The application of
glue can be limited to a relatively narrow strip, which, in FIGS. 3
and 4, is indicated as being bounded by broken lines.
The foil blank 3 is divided by two fold lines 13 into a front wall
portion 14 and two side wall portions 15 and 16. The fold lines 13
are continued by aligned groove lines 12, which are located between
the front wall 4 and the side walls 5 and 6 of the cardboard blank
1. Two box edges are formed at these groove lines and the fold
lines 13 which are exactly aligned therewith when the folding box
is erected.
Thinned-down areas 17 in the foil blank 3 are provided respectively
at four overlap points between the two blank portions 1 and 3 in
the area of the two previously mentioned box edges; said
thinned-down areas will be explained with particularity
hereinafter.
The invention is basically applicable to all types of folding boxes
and other foldable packaging units, as for instance foldable
slip-on covers; this to the extent that overlap between cardboard
and plastic foil occurs in the area of box edges. In order to
illustrate, to that extent, the universal utilizability of the
invention, a type of folding box considerably deviating from the
window folding box according to FIG. 1 is shown as a blank in FIG.
2 with the help of its blank. Here we are delaing with a folding
box which has the approximate shape of a cube after gluing,
erecting and closing on both sides. Here no window opening is
provided in the first blank 18 consisting of cardboard. Rather, the
second blank 25, fabricated from transparent stiff plastic foil,
constitutes, with its external outline, a portion of the overall
blank, so that complete wall surfaces, or wall surfaces continuous
throughout one box edge length, consisting of transparent plastic
foil are formed in this folding box.
The first blank 18 comprises the rear wall 19, two half side walls
20, 21, a smaller sealing flap 22, a larger sealing flap 23 and
four half dust tabs 24. The foldability between these parts is
again made possible by the groove lines 12 pressed into the
cardboard.
The second blank 25, fabricated from transparent stiff plastic
foil, comprises the front wall 26, two side wall parts 27, 28, a
larger sealing flap 29, a smaller sealing flap 30 and four dust tab
parts 31 connected to the side wall parts 27, 28.
The foldability of the described foil parts is again assured by the
bend lines 13 located in the foil. Insert tabs 32 are located at
the sealing flaps 29, 30, which engage slits 33 when the folding
box is closed; said slits 33 are located in the sealing flaps 22,
23 of the cardboard blank part 18. As is evident, the sealing flaps
22 and 29, on the one hand, and the sealing flaps 23 and 30, on the
other hand, interact when the folding box is closed. Since the
smaller sealing flap 22 of the cardboard blank part 18 is only half
as large as the sealing flap 23 constituting the box base, the
upper box closure also permits a view inside of the box because of
the transparent sealing flap 29.
As FIG. 2 furthermore shows, the two blank parts 18 and 25 are
glued to each other so as to overlap, which is indicated by the
dotted surface area. Herein, the portions of the foil blank 25
which are designed to be larger, as far as the area is concerned,
namely, the side wall portion 28 and the two connected dust tab
portions 31, overlap the corresponding portions 20 and 24 of the
cardboard blank part 18. The gluing between the two blank portions
occurs in the dotted surface area on the insides parts 20, 24.
Correspondingly, the half of the side wall 21 and the half dust
tabs 24 connected thereto of the cardboard blank portion 18 are
glued in an overlapping fashion to the side wall part 27 and the
dust tab parts 31 connected thereto of the foil blank portion 25.
The overlap limits are indicated in FIG. 2 by means of two broken
lines.
Also in the case of this folding box, overlap points in the area of
the four box edges are located in the two existing overlap areas of
the two blank portions 18 and 25, at which respectively, one bend
line 13 is continued in a precisely aligned manner by a groove line
12. At these overlap points, four thinned-down areas 17 in the foil
material of the foil blank portion 25 are again provided in
accordance with the invention. The design and arrangement of the
thinned-down areas 17 is now explained with particularity.
In this connection, reference is made, first of all, to the FIGS. 3
and 4, in which, respectively, one single overlap point between the
cardboard blank portion 1 or 18 and the foil blank portion 3 or 25
is shown. As can be seen, the groove line 12 in the cardboard blank
portion is exactly aligned with the bend line 13 in the foil blank
portion, so that a folding edge of the box is formed during the
folding process which passes in a straight line through both
materials. In the region of this box edge, the foil blank portion 3
(25) includes the thinned-down area 17, which extends across the
entire overlap length and slightly beyond. The thinned-down area 17
comprises an approximately rectangular outer periphery, the longer
central axis of which coincides with the groove line 12 and the
bend line 13.
As can be seen from the schematic sectional illustrations of the
FIGS. 5 to 9, the blank portion 3 (25) is thinned-down to a
fraction of its original foil thickness in the region of the
thinned-down area 17, wherein the thickness is smallest in the
center of the thinned-down area 17, i.e. in the region of the
groove line 12. The cross-sectional formations of the thinned-down
areas 17 illustrated in FIGS. 5 to 9 extend essentially over the
length of the areas 17. Furthermore, it can be seen from the FIGS.
5 to 9 that the thinned-down areas 17 diminish in thickness
starting from their side edges 34 towards the center thereof. The
reduction in thickness differs in the embodiments shown.
At the side edges 34 of the thinned-down areas 17 small beads are
indicated in the FIGS. 5 to 9 and 12, which occur due to material
migration from the thinned-down area during the fabrication of the
thinned-down areas. The dimensions of these beads can be held
within limits by means of suitable measures, so that they do not
interfere even if the foil blank portion 3 (25) is glued together
with the cardboard blank portion 1 (18) on the side carrying the
beads. In the example according to FIG. 12, the surface of the foil
blank portion not comprising the beads is glued to the cardboard
blank portion.
The thinned-down area 17, viewed in cross-section, can be bounded
on one side in an arch-shaped manner as is illustrated in the FIGS.
5 and 6. In the example according to FIG. 7 the thinned-down area
17 is bounded on one side by two inclined planes 35 meeting in the
center. An embodiment shape is illustrated in FIG. 8, in which the
thinned-down area 17 is bounded on the one side by two outer
inclined planes 36 and a central flat plane 37. FIG. 9 finally
illustrates an embodiment of the thinned-down area 17 including
flat surfaces 38 to 40 arranged in a step-shaped manner on one side
of the foil. In each of the embodiments according to the FIGS. 5 to
9, the thickness of the thinned-down area decreases from the side
edges 34 towards the middle.
The border surface profilings of the thinned-down areas described
above are achieved by an appropriate design of the tool provided
for fabrication of the thinned-down areas. The application of the
thinned-down area 17 can occur simultaneously with the placement of
the bend lines 13 in one work process, and indeed with the help of
processes for the application of the bend lines. High frequency
heating with the simultaneous application of pressure is
principally used for this purpose, by means of which particularly
pliable soft bend edges are generated. Usable results are, however,
also achieved by simultaneous hot stamping of the thinned-down
areas 17 and the bend lines 13. Herein, the fabrication of the
thinned-down areas as well as the bend lines 13 occurs
appropriately by action on one side of the plastic foil. The
application of the bend lines 13 with the high frequency process
(DE-PS No. 25 41 324) as well as with the hot stamping process are
so well known, that they do not require any further explanation at
this time.
If the folding of the overlap points for formation of a box edge in
an embodiment of the thinned-down area 17 occurs according to one
of the FIGS. 5 and 7-9, then small wrinkles occur essentially along
the groove line 12 caused by the material upsetting in the region
of the thinned-down area 17 in direct proximity of the groove lines
12 of the cardboard blank portion 1 (18); this completely
compensates the upsetting stresses in the foil in the overlap
region of the box edge. The described process for formation of the
small wrinkles can be additionally considerably promoted, if three
parallel grooves equally spaced from each other are molded within
the thinned-down areas 17, as shown in the examples in FIGS. 4 and
6. The molding of these small grooves occurs simultaneously with
the fabrication of the thinned-down areas 17 and the bend lines 13.
As can be recognized in the example according to FIG. 4, the
central groove 42 follows directly the bend line 13, while the two
side grooves 41 and 43 are kinked at their inner ends and unite
with the central groove 42 at the junction point with the bend line
13. If the thus formed thinned-down area 17 is deformed during
folding of the folding box edge concerned, then intended folds
defined along the grooves 41 to 43 are formed, as is illustrated in
FIG. 12 in a greatly magnified manner. Because of this, the overlap
area considered here is not only folded in a particularly easy
manner, but a defined foil deformation in the thinned-down area is
generated during the stress compensation with the successful equal
appearance of all overlap areas in the box edge area after the
erection of the folding box.
FIG. 12 illustrates the typical formation of a bead 44 lying inside
in the region of the groove line 12 in the cardboard blank section
1 (18). As is evident, the surface zones of the thinned-down areas
located between the grooves 41 to 43 rise in a roof-shaped manner
from the bead 44 when the defined predetermined folds are formed;
this happens if parallel grooves 41 to 43 are placed in accordance
with FIG. 4 and 6. The extent of this roof-shaped predetermined
folding generated inwards however diminishes in the inner end zone
of the grooves 41 to 43, in which the grooves converge towards the
junction point at the bend line 13; this phenomenon causes again an
approach of the foil material towards the bead 44. The
predetermined fold formation therefore does not lead to the
formation of holes in the edge transition region between the folded
bend lines 34 and the groove lines 12, as is illustrated in the
FIGS. 10 and 11.
As can be seen in FIGS. 10 and 11, it is not necessary that the
inner end region of the thinned-down area 17 projects essentially
beyond the cardboard edge. In spite of that all the stresses
arising during folding are compensated by the thinned-down area 17
in such a way, that neither a perturbing deformation of the foil in
the visible region nor a tearing of the cardboard material in the
zone of the groove line 12 occurs. Bend line 13 and groove line 12,
rather, constitute a smoothly continuous box edge, which is also
nearly free of steps at the transition point between the carton and
the foil in the edge region. The folding box thus meets all
requirements including aesthetic ones.
The placement of parallel grooves 41 to 43 was only described with
reference to an arc-shaped delimitation of the thinned-down area
17, however the thinned-down area 17 can also be provided with
grooves 41 to 43 corresponding to the embodiments illustrated in
FIGS. 7 to 9. A particularly favorable easy foldability in the
region of the grooves 41 to 43 results if the foil residual
thickness of the central groove 42 is smaller than that of the two
corresponding side grooves 41 and 43.
If stiff plastic foils are used for the fabrication of packagings,
particularly folding boxes, foil thicknesses are utilized which lie
in the region between 200 and 400 .mu.m. For this thickness range,
it has been found to be advantageous if the thinned-down areas 17
are formed in such a way that the minimum thickness of the central
region of the thinned-down areas amounts to approximately 100
.mu.m. The placement of grooves 41 to 43 reduces the minimum
thickness at the grooves considerably. One obtains good results if
the central groove 42 results in a foil residual thickness of
approximately 30 .mu.m, while the foil residual thickness at the
two side grooves 41 and 43 amounts to approximately 60 .mu.m.
In the embodiment illustrated in FIG. 13 depicting the
cross-sectional shape of the thinned-down area 17, we are also
dealing with a schematic sectional presentation. Previous
statements dealing with the embodiment examples in FIGS. 5 and 9
apply also to FIG. 13 to the extent that no deviating statements
are made in the following text. Thus, the additional placement of
parallel grooves 41 to 43 according to FIG. 4 is not provided for
the embodiment in FIG. 13. In addition, the above statements
concerning the minimum thickness in the central region of the
thinned-down areas do not apply.
As is recognizable, a flat central strip 45 is located in the
thinned-down area 17, the width of which is indicated by the
dimension lines given the reference number 47. This central strip
45 extends across the entire length of the thinned-down area 17 and
covers the assigned groove line 12 in the cardboard blank portion
when the foil blank portion 3 (25) is joined with the cardboard
blank portion 1 (18). Since the central strip 45 extends across the
entire length of the thinned-down area, it is directly contiguous
to the associated bend line 13 in the foil blank portion 3 (25).
The central strip 45 has a very small constant foil residual
thickness of 40 to 60 .mu.m throughout. Good folding results are
achieved with a residual thickness of 55 .mu.m. The small foil
residual thickness indicated applies to a thickness of plastic foil
of between 200 and 400 .mu.m which is to be used for the foil blank
portion 3 (25). The width 47 of the central strip 45 lies between
one-third to one-sixth of the width of the thinned-down area 17,
which can amount to approximately 8 mm. A corresponding width of 8
mm for the thinned-down area 17 is also sufficient for the examples
described previously. Good results were achieved with a width of
the central strip 45 of between 1.5 and 2 mm.
Transition surfaces 46 arched in a concave manner adjoin the
central strip 45 on both sides in a stepless fashion; said
transitional surfaces 46 terminate at the side edges 34 of the
thinned-down area 17. When folding the glued-together blanks, it
has been shown that the desired small wrinkles occur in the region
of the central strip if the cross-sectional shape is according to
that shown in FIG. 13; this results in an approximate configuration
as shown in FIG. 12, even if the glue between the two blanks is not
interrupted at the thinned-down areas 17. In this case micro
wrinkles form which, in actual practice, rest tightly at the bead
44.
The overlap spots depicted in truncated form in the FIGS. 14, 16
and 18 can basically be designed in all known types of folding
boxes as illustrated in said figures, provided they are composed
out of a first blank portion 1, which, for instance, is constituted
by cardboard and a second blank portion 3 from transparent thick
plastic foil. Such composites of folding boxes can be designed
resembling a window folding box, as indicated by window openings 2
in FIGS. 15, 17 and 19 at a comparatively smaller scale, or they
can comprise a larger plastic material part compared to a window
folding box, which extends across several wall portions possibly
including adjacent sealing flaps and dust tabs. The folding boxes
considered here have, in common, the overlap between the cardboard
blank part 1 and the foil blank part 3, wherein both blank parts
are glued together, and indeed the cardboard blank part 1 on its
inside and the foil blank part 3 on its external side. The
overlapping gluing is indicated in a dotted manner in the FIGS. 14,
16 and 18 and does not have to extend across the entire overlap
area. The gluing can also be executed in a strip-shaped manner, as
it is indicated in the above-named figures by the broken lines
extending parallel to the edges of both blank parts 1 and 3.
In case of the window folding box depicted in the FIGS. 15, 17 and
19, the foil blank part 3, and with it also the window opening 2,
extend across at least two abutting wall surfaces of the folding
box, namely, across the front wall 4 and the side wall 6 in the
illustrated embodiment. Accordingly, the foil blank part 3
comprises a front wall portion 14 and a side wall portion 16, which
abut at the bend line 13. The reference number 7 designates the
rear wall, and the reference number 9, the lower sealing flap of
the folding box. The front wall 4 and the side wall 6 of the
cardboard blank part 1 are located on both sides of the groove line
12 pressed into the cardboard. In the drawings, only one groove
line 12 of the folding box and only one section of a bend line 13
is illustrated. It can, however, be seen that the bend lines 13 and
the groove line 12 are exactly aligned with each other if the
folding box blank (FIGS. 14, 16 and 18) is in a flat resting
position; after gluing, erecting and closing of the folding box,
said bend line 13 and groove line 12 form a continuous box edge
(FIGS. 15, 17 and 19).
At all overlap spots existing at the box edges, of which only one
is depicted in the drawings, the plastic foil material, consisting,
for instance, of polyvinylchloride, is thinned-down to a fraction
of its original foil thickness of approximately 200 to 400 .mu.m in
the zone of a thinned-down area 17, wherein the thickness within
the thinned-down area 17 is smallest in the center, that is in the
region of the groove line 12. The thinned-down area 17 is delimited
by edges 34 on the sides, at which also the gluing between the
cardboard blank part 1 and the foil blank part 3 can end. As is
seen, the thinned-down area 17 extends across the entire overlap
length of both blank parts 1 and 3.
The placement of the thinned-down area 17 can occur simultaneously
with the placement of the bend line 13 in one single work process
using procedures common for placement of bend lines, for instance
by high frequency heating of the foil with simultaneous application
of pressure. Bend lines produced in this manner yield particularly
bendable soft bending edges.
The thinned-down area 17 compensates for stresses and consequent
deformations occurring in the foil material at the overlap spots
during folding, without which the cardboard material is stretched
so that it tears at the edge overlap points. Residual stresses can
occur particularly with thicker foils during folding in the
transition zone between the thinned-down area 17 and the original
foil material of the wall parts 14 and 16; this is because the bend
line 13 has the desirable tendency to migrate somewhat towards the
outside during the folding process, in order to form a practically
stepless continuous box edge by alignment with the groove line
12.
It is necessary to avoid damage of the cardboard blank part at the
boundary to the viewing area of the window opening 2 as well as
possible warping in the area of the foil material of the wall parts
15 and 16 adjacent to the overlap spot. Therefore, to absorb such
residual stresses, a line-shaped incision 48 is made in the foil
blank part 3 in the embodiment form according to the FIG. 14, 15 at
the juncture between the bend line 13 and the thinned-down area 17,
said incision passing through the material thickness of the foil
blank part 3. The incision 48 protrudes on both sides beyond the
bend line 13 and extends parallel to the near edge of the cardboard
blank part 1. The smaller the distance of the incision 48 from the
mentioned neighboring edge of the cardboard blank part 1, the less
prominent is the incision when the folding box is erected, as is
shown in FIG. 15. In this case, because of the explained outward
migration of the bend line 13 during the folding process, there is
generated only a very small downwardly oriented opening (referred
to the illustration according to FIG. 15) at the separation point
at the box edge defined by the incision 48.
In the embodiment of the separation discernible from FIGS. 16 and
17, said separation is constructed as a circularly-shaped hole
cutout 49, which separates the bend line 13 from the thinned-out
area 17 and is only in outline overlapped by the cardboard blank
part 1. The hole cutout 49 protrudes with approximately equal
surface regions towards both sides beyond the bend line 13, as can
be discerned from FIG. 16. It has been seen that a comparatively
small diameter of the hole cutout 48 in relationship to the width
of the thinned-out area 17 is sufficient in order to cause the
above-mentioned additional stress equalization at the junction
point between the bend line and the thinned-out area 17 to occur.
Because of the small diameter, the hole cutout 49 is scarcely
noticeable when the folding box is erected, as is made clear in
FIG. 17.
In the embodiment according to FIGS. 18 and 19, the hole cutout
constituting the separation is constructed in the shape of an
ellipse 50, longer axis of which extends parallel to the
neighboring edge of the cardboard blank part. In this case also the
ellipse 50 protrudes with approximately equal surface areas to both
sides of the bend line 13 and is only slightly overlapped by the
cardboard blank part 1. The smaller diameter of the ellipse is made
to be so small, that the box edge of the errected box constituted
by the bend line 13 and the groove line 12 is only slightly
interrupted. In the illustrated example, the largest diameter of
the ellipse 50 is considerably smaller than the width of the
thinned-out area 17, which, because of the increased scale in the
FIGS. 14, 16 and 18, appears to be in any case wider than it is in
actual practice.
The geometric versions of the hole cutout discernible from the
FIGS. 16 and 18 are only given by way of preferred examples.
Deviating geometric configurations such as, for instance, polygons
are also possible if only an approximately symmetrical arrangement
with reference to the bend line 13 and the groove line 12 is
provided and the other indicated conditions are observed.
* * * * *